[For a brief period after Newsletter 27 in the year 2002, we posted to LexiLine without giving a specific Newsletter number, and then resumed normal numbered postings with Newsletter 28. Hence the interceding postings (with related topics sometimes combined in one posting) are here named 27-A, 27-B, 27-C, etc.]
Jean Buffum sent the following posting concerning "Potential new method for verifying dates of megaliths?"
The main thing of relevance to your work, at end of article linked below is "...the cosmogenic dating method developed by Cerling to date basalt flows and other landforms in the Grand Canyon. The technique measures how long a surface has been exposed to cosmic rays from space."
Michael Mandeville, (who I think may be subscribed to Lexiline Newsletter) suggested in one of his web site newsletters that the dating method might be worth investigating for possible application to dating of ancient monumental architecture......so perhaps might have potential as additional method of verifiying some of your propositions.
See article titled, "Is the Grand Canyon a Geologic Infant?" ...
[Update, 2006: the URL originally given is no longer available in 2006 but see http://snipurl.com/yqnr, a snipped URL of the Google cache of the article by Ed Stiles.]